=SCIENTIFIC IDEAS OF TO-DAY.= A Popular Account, in Non-technical Language, of the Nature of Matter, Electricity, Light, Heat, Electrons, _&c. &c._ By CHARLES R. GIBSON, F.R.S.E., Author of “Electricity of To-Day,” _&c._ “Supplies a real need.... Mr. Gibson has a fine gift of exposition.”—_Birmingham Post._ =ASTRONOMY OF TO-DAY.= A Popular Introduction in Non-technical Language. By CECIL G. DOLMAGE, LL.D., F.R.A.S. With frontispiece in colours, & 45 other illustrations. “Dr. Dolmage has absolutely kept to his promise to introduce the reader to an acquaintance with the astronomy of to-day in non-technical language.”—_Saturday Review._ =ELECTRICITY OF TO-DAY.= Its Work and Mysteries Explained. By CHARLES R. GIBSON, F.R.S.E. “Mr. Gibson has given us one of the best examples of popular scientific exposition that we remember seeing. His book may be strongly commended to all who wish to realise what electricity means and does in our daily life.”—_The Tribune._ =ENGINEERING OF TO-DAY.= A Popular Account of the Present State of the Science, with many interesting Examples, described in Non-technical Language. By THOMAS W. CORBIN. With 73 illustrations & diagrams. “Most attractive and instructive.”—_Record._ “The descriptions which are given of various types of engineering structures and work are excellent.”—_Yorkshire Observer._ “Altogether a most delightful book.”—_Literary World._ =MEDICAL SCIENCE OF TO-DAY.= A Popular Account of the more recent Developments in Medicine & Surgery. By WILLMOTT EVANS, M.D., B.S., B.SC. (Lond.), F.R.C.S. (Eng.), Surgeon to the Royal Free Hospital. =MECHANICAL INVENTIONS OF TO-DAY.= An Interesting Description of Modern Mechanical Inventions told in Non-technical Language. By THOMAS W. CORBIN, Author of “Engineering of To-Day.” With 95 illustrations & diagrams. SEELEY, SERVICE & CO. LIMITED AUTHOR'S NOTE A great deal has been written about the General Post Office in newspapers and magazines, but the books on the subject are comparatively few. And these volumes are either exhaustive historical treatises, such as Mr. Herbert Joyce's _History of the Post Office_, or more popularly written descriptions of Post Office life and work of the character of Lewin's _His Majesty's Mails_ or J. W. Heyde's _Royal Mail_. Mr. Joyce's work, however, carries us no farther than the eve of penny postage, while the other books were written too long ago to be a guide to the Post Office of to-day. It is within the last twenty years that the Department has made the most rapid strides in the extension of its activities, and it is this period especially which is without an historian.